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The Delta COVID-19 variant is spreading in Sydney, prompting fresh restrictions and concern from authorities. Here is what we know about it.
The variant was the second spotted in India. Formerly known as B1.617.2, it is one of two sub-variants of the B1.617 lineage (the other being the Kappa variant, which spread in Melbourne last month).
Evidence suggests it is substantially more transmissible than the Alpha variant, which was already more transmissible than the virus that came originally out of Wuhan.
It is the second-most common variant in NSW’s quarantine system, after the Alpha variant. There were 48 cases of the Delta variant recorded in returned overseas travellers to the end of May, although none since.
Outside the state’s quarantine system, Health Minister Brad Hazzard said Delta was a spreading “gold medallist”, with transmission occurring at Bondi Junction Westfield among people who CCTV showed had only passed each other.
“Last year, we talked about this particular virus when it first came to our shores as being obviously dangerous but it wasn’t a long jumper and it wasn’t a high jumper,” Mr Hazzard said on Tuesday.
“[But] we also need to recognise that the Delta variant of the COVID virus is actually a gold medallist when it comes to jumping from one person to another - it is a long jumper.”
Of course, this is not always the case: the eastern suburbs man known for visiting many barbecue stores last month was infected with the Delta variant and transmitted it to only his partner.
ANU epidemiologist Meru Sheel said the transmissibility of Delta was “really complex”, involving both Delta’s higher “secondary attack rate” - the number of contacts who become cases - and the individual’s viral load.
Dr Sheel said it was important to monitor how many cases were vaccinated and how many of their contacts are vaccinated to understand the outbreak’s epidemiology.
There is some evidence the Delta variant may modestly cut the effectiveness of vaccines but human data from Britain suggests both AstraZeneca’s and Pfizer’s vaccines offer protection against the variant after two doses.
Pfizer’s vaccine is 88 per cent effective against symptomatic disease caused by the variant, while AstraZeneca’s vaccine is 60 per cent effective. Scientists expect both vaccines to offer much higher levels of protection against serious illness and death.
with Lucy Carroll
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